Apparatus for grading heterogeneous or granular products, such as grain, by means ofa current of air



Jan. 11, 1955 H. A. BOK 2,699,254-

APPARATUS FOR GRADING HETEROGENEOUS OR GRANULAR PRODUCTS, SUCH AS GRAIN, BY MEANS OF A CURRENT OF AIR Filed Feb. 12, 1951 INVENTOR. ABOK BY W =14 M fifforn 8 United States Patent APPARATUS FOR GRADING HETEROGENEOUS OR GRANULAR PRODUCTS, SUCH AS GRAIN, BY MEANS OF A CURRENT OF AIR Harald A. Bok, Aerdenhout, Netherlands Application February 12, 1951, Serial No. 210,460

Claims priority, application Netherlands February 24, 1950 1 Claim. (Cl. 209-137) This invention relates to an apparatus for grading heterogeneous or granular products, such as grain, oats, and oat husks, precious stones ground to a certain size and stone dust etc., by means of a current of air, an airblowing fan preceding a separation zone and an aspirator or a cyclone following said separation zone, which aspirator or cyclone in conjunction with said fan forms a closed air circuit.

The object of this invention is to provide an apparatus of compact construction, adapted to be accommodated as a unit in a casing common to all or substantially all of the elements of the apparatus, which apparatus operates efliciently and rationally.

To this end a separation zone is arranged in the outlet of the fan and a separating chamber merges directlyi. e. without an intermediate connecting channel-into an upright flue leading to a horizontal cyclone, the wall of said flue forming on the one hand a partition between the cyclone and said flue and on the other hand a partition between said flue and a chute through which the material to be graded is supplied.

When a separation zone formed by a number of streamlined adjustable louvres is arranged in the outlet channel of the fan, the louvres can be constructed, according to the invention, as streamlined elements, which are so spaced apart from one another and are of such a shape as to cause the air to attain a velocity that will prevent any product from dropping through them, and which at their ends directed towards the separation zone form reflecting surfaces for heavy granules. Now it is no longer necessary to have a sieve follow the louvres. The streamlined shape can be realized by giving the elements a substantially pear-shaped crosssection, the blunt end of which forms a reflecting surface or a rebounding surface for heavy granules, which end, therefore, is turned towards the separation zone.

According to the invention the separating chamber following the separation zone preferably comprises a wall portion located above an outlet slot for heavy particles, which wall portion is so located that particles which as regards their weight form borderline cases are thrown back into the current of air by their impinging against said wall portion, which may happen several times, until they are either discharged through the outlet slot or are entrained with the lighter particles into the flue.

Finally the horizontal cyclone from either side of which the air is returned to the suction side of the fan, can be provided with an air port extending over the entire or substantially the entire width of the cyclone, which port is formed by an air gap in a horizontal drum adapted to be turned about its axis, said air gap being ad ustable by turning said drum. The entire control of the aspirator 1S efiected, by adjusting said air gap, assuming that the number of revolutions of the fan remains constant. This construction contributes towards a simple and compact build of the whole grading apparatus.

The invention is illustrated hereinafter with reference to the accompanying drawings showing by way of example an embodiment of the apparatus according to the invention. In these drawings:

Fig. l is a vertical cross section of a grading apparatus according to the invention and Fig. 2 shows, on a slightly larger scale, a section of a portion of the apparatus according to line IIII in Fig. l, which section is broken in the middle and is normal to the section according to Fig. 1.

In Fig. l, the reference numeral 1 designates a feeding chute for the products to be separated, which products are supplied over the entire width of this chute to an inlet slot 2. On leaving said slot 2 the products enter an air channel 3, the lower end of which communicates with the outlet side of a fan 4.

At the place where the outlet side of the fan 4 merges into the air channel 3 some streamlined louvre elements 5 are provided which define gaps through which the air can pass. As appears from the drawing the elements 5 are about pear-shaped in cross-section and have their blunt ends which form a reflecting surface for heavy granules or the like, directed towards the separation zone. These elements are pivotally mounted at 6 and can be secured in the desired positions. The current of air produced by the fan passes between the elements 5, the velocity of this air being so controlled that even the heaviest particles of the product dropping out of the slot 2 towards the outlet slot 7 cannot drop vertically downwards against the current of air. The cross-sectional area of the air channel close above the elements 5 is so large that the veloc ty of the air decreases to such an extent that only the light particles of the product are entrained. The heavy particles immediately pass through the outlet slot 7 to be discharged through a channel 8. The light particles are entrained by the air and will come into a narrowing portion 9 of the air channel, Where the velocity of the air is greater than in the wide portion located thereunder, so that are certain to be entrained light particles by the air.

they too distogether with 4 are of the same width as the air channel 3.

The air and the light particles which are sucked into the fan through channels 13 and 14 (Figure 2). The air, therefore, circulates in a closed circuit.

In order to ensure that the air is regularly discharged from the cyclone to the fan, the cyclone is provided with an air gap 15 extending over the entire or substantially the entire Width of the cyclone, which gap is formed by a drum 17 adapted to be turned about the horizontal shaft 16. By turning this drum at 18, the air gap 15 can be opened or closed to a greater or less drum can be fixed in the position selected. tion can be attended by the adjustment desired number of revolutions.

If desired the apparatus can be operated with two or more fans with matching means for guiding the air.

I claim:

An apparatus for grading heterogeneous or granular products by means of an air stream, comprising a separation chamber, a blowing fan having an outlet, a plurality of louvres forming a separation zone at one end of said separation chamber and being located within the outlet of said fan, a horizontal cyclone, recycle channels for said fan, an upright channel merging into said separation chamber and leading to said horizontal cyclone connected to the fan by recycle channels so as to form a closed air circuit, a feed chute for the material to be graded, said chute having at its lower end a discharge opening entering into said separation chamber, an outlet for heavy particles in the wall of the separation chamber opposite said discharge opening, the wall of said upright channel forming a partition wall between said upright channel and said cyclone and forming a partition between said channel and said feed chute, said separation chamber at a distance from said louvres narrowing towards said 4 upright channel, said upright channel having a constant 258,495 Sternberg May 23, 1882 cross-sectional area up to the point where it merges into 857,065 Holgate June 18, 1907 said cyclone, and a wall portion of said separating cham- 1,298,086 Pallonsch Mar. 25, 1919 her located above said outlet for heavy particles, said 1,597,261 Bishop Aug. 24, 1926 wall portion being located in the path of particles which 5 1,659,695 Mayhew Feb. 21, 1928 by weight are intermediate between heavy dischargeable 1,903,046 Hunter Mar. 28, 1933 particles and light separated particles to throw said inter- 1,987,640 Rothgarn J an. 15, 1935 rnediate particles (packuinto the curlrelnt of air lllay (iirn- 2,591,396 Bergner Apr. 1, 1952 pinging against sai wa portion unti t ey are eit er ischarged through the outlet slot or are entrained with 10 FOREIGN PATENTS the light particles into said upright channel. 358,329 Great Britain Oct. 8, 1931 441,809 Great Britain Jan. 27, 1936 References Cited in the file of this patent OTHER REFERENCES UNITED STATES PATENTS 15 Transactions of the Institution of Mining Engineers, 8,008 Hollingsworth Apr. 1, 1851 vol. LXXXIX, part 6, pages 302-311. Printed by A.

33,231 Beach Sept. 10, 1861 Reed & Co., Ltd., Newcastle-upon-Tyne, 1935. 

